The present invention relates generally to a vacuum control device used for holding a workpiece, and more particularly, to a vacuum control device which may be activated by placing the workpiece on the vacuum control device without having to first manually invert the vacuum control device.
Vacuum worktables have been designed and used to hold a variety of workpieces for different machining operations including cutting, routing, sawing, and grinding. To prevent the workpiece from moving during the machining process, worktables have been constructed with vacuum pumps that pull air through the worktable to hold the workpiece in place. An example of such a worktable is disclosed in U.S. Pat. No. 5,222,719, to Effener, et al. The worktable disclosed in the Effener patent includes a plurality of recessed openings distributed over the worktable surface. A pod may be placed within each of these recessed openings.
The pod disclosed in the Effener patent is circular with a central boss that extends from a base in an offset manner. The base has a central opening to allow air to pass therethrough. The pod may be placed within the recessed opening in either an activated or deactivated position.
In the activated position, the base sets over the recessed opening with the central boss extending away from the worktable. The air can then pass through the central opening and into the worktable through vent openings positioned adjacent to the walls of the recessed opening when the vacuum pump is started. With air flow, a worker can set a workpiece atop of the central boss to form vacuum between the workpiece and the pod.
A worker must manually invert the pod in the deactivated position to prevent air from passing through the pod to create the vacuum. In the deactivated position, the base sets over the recessed opening with the offset central boss extending to the floor of the recessed opening. This forms an annular chamber between the offset central boss and the wall of the recessed opening. The annular chamber is the only space that communicates with the vented opening and contains the only air that will be evacuated when the vacuum pump is started.
Other manufacturers have developed similar pods to regulate vacuum pressure. Carter Products Company, Inc. of Grand Rapids, Mich. developed a pod that utilizes a ball as a valve to regulate air flow. The ball sets inside a central chamber open to and surrounded by an annular outer chamber. Air may pass through openings at each end of the central chamber. However, a ball check is placed over an opening at one end of the central chamber and guides the ball over the opening when the pod is placed in the deactivated position. The ball closes this opening to prevent air from passing through the pod to the worktable, thus preventing a vacuum to form between a workpiece and the pod.
The Carter pod is placed in the activated position when a worker manually inverts the pod in one of the recessed openings of the worktable. In the activated position, the ball falls to the side of the airflow opening, allowing air to pass through the pod. A worker may then place a workpiece atop of the pod to form a vacuum between the workpiece and worktable. Although a vacuum is eventually formed, the vacuum pump must first evacuate the air from both the central chamber and the surrounding annular chamber to reduce the internal pressure of the pod enough to create the vacuum.
One of the disadvantages and limitations of the pre-existing pods disclosed above is that manual labor is required to activate or deactivate the pods. All pods of the prior art require a worker determine where the workpiece will fit over the worktable and what pods must be activated to safely and securely hold the workpiece in place. In those areas of the worktable where the worker determines no vacuum is required, the worker must manually invert the pods from the activated to deactivated position. The worker is then required to position the workpiece over the activated pods and if any changes are necessary, the worker must repeat this process. This is a time consuming and tedious matter that results in lost time and money.
Further, the pods of the prior art include multiple chambers which must be evacuated before a sufficient negative pressure is created to draw a vacuum between the pods and a workpiece. Multiple chambers create a larger total internal volume. The greater the volume, the longer it takes to remove the gases from those spaces to create the negative atmospheric pressure. Again, this increased waiting time translates to lost time and money.
Lastly, the pods of the prior art do not have a mechanism that adequately prevents the pods from scratching or denting the workpiece. Many workpieces are made from expensive and fragile materials susceptible to scratching, denting or breaking. These workpieces are often damaged during the machining process from the pods which are made of rigid materials.
To overcome the disadvantages and limitations associated with the prior art, an objective of the vacuum control device of the present invention is that it be able to regulate the vacuum pressure without requiring a worker to manually invert or flip the vacuum control device. The vacuum control device should be activated when a workpiece is placed atop of the vacuum control device and deactivated when the workpiece is removed. Further, the vacuum control device should also be able to filter out dust, dirt and other debris from the work environment so that the longevity of the products can be sustained.
Another objective of the vacuum control device is that it be capable of setting in a recessed opening of a worktable removed from a cutting device. This would create a clear machining path and prevent damage to the vacuum control device. In the cutting position, the vacuum control device should be deactivated to prevent air from passing through the vacuum control device. The vacuum control device should also be made from a material that will not damage the cutting device if the cutting device accidentally strikes the vacuum control device when the vacuum control device is not placed in the cutting position.
As a further objective, the vacuum control device should securely set within the recessed opening in either the operating or cutting position so that the workpiece may not slide or move while being machined.
Yet another objective of the vacuum control device is that it should have a single chamber to restrict the internal volume of the vacuum control device. This should allow a rapid evacuation of air from the vacuum control device to efficiently provide sufficient vacuum to hold the workpiece securely and firmly in place so that the workpiece may be worked upon without dangerous and inefficient slipping or sliding. Further, the vacuum control device should be fitted with a mechanism to prevent air from escaping between the vacuum control device and the workpiece while providing scuff or dent resistance.
Finally, it is also an objective of the vacuum control device that all the aforesaid advantages and objectives be achieved without incurring any substantial relative disadvantage.
The disadvantages and limitations of the background art discussed above are overcome by a vacuum control device for holding a workpiece that is taught by the present invention.
The vacuum control device of the present invention includes a body that may be securely placed within a recessed opening of a worktable. The body has two sides a support side and a seating side, both separated by a flange. The flange extends outwardly from the body and is constructed to rest within a mating ledge surrounding each recessed opening. Either the support side or the seating side can fit within the recessed opening.
The body surrounds an interior chamber that is open on the seating side and is partially closed by a top wall on the support side. The top wall includes a stem aperture flanked by at least one vacuum hole, both providing an opening to the interior chamber. The top wall may be either contiguous with the body or a separate piece attached to the body.
The interior chamber houses a valve that controls vacuum pressure by regulating the passage of air through the interior chamber. The valve includes a plunger and a spring. The plunger has a stem and a vacuum stop. The stem protrudes through the stem aperture of the top wall and extends beyond the outmost plane of the vacuum control device. The vacuum stop is either connected to the stem by a fastener or is contiguous with the stem. The vacuum stop is constructed to prevent the plunger from completely passing through the stem aperture, and to cover each vacuum hole when pressed against the top wall.
The spring is partially compressed and situated behind the plunger in the interior chamber to force the plunger firmly against the top wall and obstruct each vacuum hole. The spring maintains its partially compressed state within the passage by resting between the plunger and a base. The base covers the opening to the interior chamber at the seating side and is removably connected to the body by one or more removable fasteners. The base should be rigid enough to withstand the force exerted on the base from the spring and allow air to pass through the base, while preventing the passage of dirt, dust and other debris. This may be accomplished by a porous base or filter.
The vacuum control device regulates the flow of air when used in combination with a workpiece and a worktable. The vacuum control device is placed in a position to allow air to pass through the interior chamber and into the worktable when the seating side is placed into the recessed opening with the support side rising above the worktable. A worker may then start a vacuum pump connected to the worktable which pulls air through the recessed opening and the base to evacuate air from the interior chamber. However, the vacuum control device prevents air flow from outside the vacuum control device in this position because the spring forces the vacuum stop against the top wall to obstruct each vacuum hole.
A worker may then activate the vacuum control device by placing a workpiece upon the vacuum control device. The weight of the workpiece depresses the stem and separates the vacuum stop from the top wall to clear each vacuum hole. Air can then pass through each vacuum hole from the space between the workpiece and the vacuum control device through the interior chamber. As air evacuates from between the workpiece and the worktable, a negative atmospheric pressure is created which causes a vacuum to form between the workpiece and the support side. The vacuum firmly holds the workpiece to the vacuum control device so that the workpiece may be machined cleanly, safely and efficiently.
When a worker lifts the workpiece from the vacuum control device, the spring again forces the vacuum stop against the top wall to obstruct each vacuum hole and deactivate the vacuum control device. The spring is allowed to force the plunger against the top wall without the weight of the workpiece because the spring is in a partially compressed state.
A vacuum seal between the workpiece and the body may be strengthened by a seal ring. The seal ring may be in the form of an o-ring that sets atop of the support side or a cover that fits over the support side. The seal ring eliminates any gaps between the workpiece and the vacuum control device caused by surface irregularities on the workpiece. The seal ring may be made from pliable plastic, rubber or other similar material that is impervious to air and will help prevent scratching, scuffing and denting the workpiece.
To maintain a clean interior chamber and valve mechanism, a filter may be used to prevent dirt, dust and other debris from passing through each vacuum hole. The filter may be placed over the surface of the top wall opposite the interior chamber so that it covers each vacuum hole. The filter should also include a matching stem aperture so that the stem may protrude from the interior chamber. The filter may be secured to the vacuum control device by being placed between the top wall and the seal ring. The filter may be of the same porous material as the base with pores large enough to allow air to pass through the filter but prevent dirt, dust and other debris from fouling the interior chamber and valve mechanism.
The vacuum control device may also be positioned in a cutting position to prevent the vacuum control device from being damaged by the machining tool and to prevent damage to the machining tool. In the cutting position, the support side is placed within the recessed opening with the seating side rising above the surface of the worktable. The seating side should have a height less than the support side as measured from the flange if the vacuum control device is to be used in the cutting position. The height difference will allow a space to form between the seating side and a workpiece resting on the support side of an adjacent vacuum control device. This space provides a path for the machining tool as it cuts through the workpiece.
Thus, it may be seen that the vacuum control device of the present invention overcomes the disadvantages and limitations associated with the prior art by providing the aforesaid characteristics. The vacuum control device is able to regulate the vacuum pressure without a worker having to manually invert or flip the vacuum control device. Further, the vacuum control device is able to filter out dust, dirt and other debris from the work environment to sustain the longevity of the vacuum control device and the worktable.
In addition, the vacuum control device is capable of being set in a recessed opening of a worktable in a cutting position, removed from the cutting path. When the vacuum control device is in the cutting position, a machining path is then created. This prevents damage to the vacuum control device and the machining tool. The vacuum control device is also made from material that will not damage the cutting device should cutting device accidentally hit the vacuum control device.
Furthermore, the vacuum control device rests securely within the recessed opening in both the operating position and the cutting position. This prevents the workpiece from sliding or moving while being machined and eliminates any safety or inefficiency problems associated with other vacuum control devices that slip and slide.
Also, the vacuum control device has only the interior chamber between the worktable and the workpiece. The air from the interior chamber can be evacuated rapidly to create a sufficient vacuum to hold a workpiece securely and firmly in place so that the workpiece may be worked upon without dangerous and inefficient slipping or sliding. Further, the vacuum control device can be fitted with a seal ring to prevent air from escaping between the vacuum control device and the workpiece. The seal ring also provides scuff and dent resistance. Finally, all of the aforesaid advantages and objectives are achieved without incurring any substantial relative disadvantage.
The above brief description sets forth rather broadly the more important features of the present invention so that the detailed description that follows may be better understood, and so that the present contributions to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter, which will form the subject matter of the invention. In this respect, before explaining an embodiment of the invention in detail, it is to be understood that the invention is not limited in its application. The details of the construction and the arrangements set forth in the following description are illustrated in the drawings. But, the present invention is capable of other embodiments and of being practiced and carried out in various ways, as will be appreciated by those skilled in the art. Also, it is to be understood that the phraseology and terminology employed herein are for description and not limitation.